1. Field
Disclosed herein are a protective film and an encapsulation material comprising the protective film. More specifically, the protective film is produced by coating alternate layers of a polysilazane-based polymer and a flexible polysiloxane-based polymer wherein the polysilazane-based polymer is cured at low temperature to form silica, thereby achieving high hardness and high transmittance. The protective film has improved adhesion at the interface between the respective coating films to prevent permeation of moisture and oxygen through the protective film. In addition, the protective film can be easily produced by low-temperature wet processes.
2. Description of the Related Art
In general, protective films are used to prevent oxygen and moisture from permeating from the outside environment, to assist in maintaining the characteristics of materials contained therein. Such protective films can be used as encapsulation thin films for display devices and as moisture barrier layers for flexible substrates. At present, encapsulation thin films for display devices and moisture barrier layers for flexible substrates are generally produced by depositing inorganic materials to form inorganic layers and intercalating organic or polymer layers between the inorganic layers of the protective film to impart improved crack resistance or flexibility. Deposition of the inorganic materials, however, requires the use of expensive deposition equipment, batch type processes which incur considerable costs, and the intercalation of the polymer layer makes the procedure more complex.
Polysilazanes possess advantages in terms of transparency and antifouling properties. Based on these advantages, polysilazane can be applied to various coating materials for substrates requiring excellent mechanical properties (e.g., surface coating materials for automotive applications and highway soundproofing walls) and outer protective films for electronic devices. However, since polysilazane is cured to form a hydrophilic silica (SiO2) thin film, it has only a limited ability to prevent permeation of moisture.
There is therefore a need to develop protective films that have the ability to prevent permeation of moisture and are flexible.